L10 Flashcards
How are prokaryotic and Eukaryotic cells fuelled?
To fuel they need a carbon source, a means of capturing energy from chemical reactions or light to produce usable energy.
What macromolecules require the most energy to be made most to least
Protein, RNA, phospholipid, DNA, lipopolysaccharide, murein, glycogen
What are heterotrophs?
Cells that get their carbon source from organic sources
What are autotrophs?
Cells that use carbon dioxide as a carbon source
What are chemoheterotrophs?
Energy source and carbon source from organic sources. Consume organic building blocks that they are unable to make themselves. Most of their energy is from organic molecules such as sugars. Very common among eukaryotes.
What are photoheterotrophs?
Capture light energy to convert to chemical energy in cells, get carbon from organic sources. Examples include non-sulphur bacteria, green non-sulphur bacteria.
What are chemoautotrophs?
Break down inorganic molecules to supply energy for the cell. Use CO2 as carbon source. E.g. prokaryotes that break down H2S and ammonia. Live in extreme enviros
What are photoautotrophs?
Capture light energy, use CO2 as carbon source. E.g. Cyanobacteria. Use similar compounds to those of plants to trap light energy.
How is energy stored in cells?
ATP, energy carrying molecule used in cells as it can release energy very quickly
How does ATP store energy?
Capacity to harvest, store, and use energy is a universal feature of all cells. Energy is conserved intracellulaeyky in the energy rich phosphate bond of ATP.
How is ATP generated?
Through the addition of phosphate to ADP. When electrons are lost from a donor (oxidation) in a reaction involving chemical substrates (a) or light (b) the energy released is harvested to phosphorylate ADP and generate ATP. This is because electrons exist at different energy levels and movement from one energy level to a lower energy level releases energy
What happens in oxidation phosphorylation (chemotrophs)?
Electron moves from a high energy level in a chemical molecule (electron donor) to a lower energy level in another molecule (electron acceptor)
What happens in photophosphorylation (phototrophs)?
Light is used to excite photosynthetic pigments to move the electron to a higher energy state. This excited state is unstable, and the electron is transferred a lower energy level in another molecule (electron acceptor)
What is reduction?
When a substrate gains electrons (positive charge reduced)
What is oxidation?
When a substrate loses electrons
What is reducing power?
The potential of a substance to reduce another substance, that can be either by loss or gain of electrons or by addition or removal of hydrogen
How is hydrogen transferred?
Electrons in an organic redox reaction often are transferred in the form of a hydride ion - a proton and two electrons. Referred to as hydrogenation and dehydrogenation
What is dehydrogenation?
When a substrate loses electrons and protons simultaneously and they are transferred to an H-acceptance molecule e.g. NAD
How is reducing power used?
NADH+ can be oxidised to NAD+. By extracting the electrons (oxidising) of NADH+ and transporting these electrons sequentially through several membrane proteins (ETC). A proton gradient is generated across the cell membrane, which is used to generate energy.
What is Gibbs free energy?
Amount of usable energy released or consumed in a reaction
What is joules?
A measure or mechanical work that can be performed with that energy
What is the equation for work (energy calculations)?
Work = mass x velocity/time x displacement
What does it mean if delta G is positive?
If the reaction consumes energy (endergonic reaction) - formation of molecules is endergonic.
What does it mean if delta G is negative?
If the reaction released energy, (exergonic reaction) - the breakdown of molecules is exergonic
How much energy is needed to make reducing power?
Only those exergonic reactions that release at least 219 kj/mol can be used to generate reducing power (NADH+)
What is reducing power used for?
The cell can use NADH+ to phosphorylate ADP and generate ATP. ADP to ATP, requires 31KJ ; about 7 ATPs can be generated with one NADH+
What is a bomb calorimeter?
A lab instrument to measure the amount of a samples combustion heat or heat power when excess oxygen combustion occurs, used to work out the amount of energy stored in food by heating the food until it burns. The excess heat released by the reaction is directly proportional to the amount of energy contained in the food.
How can ATP be generated?
Aerobic oxidation - oxidation of glucose and oxidation of fatty acids
What is oxidation of glucose?
When glucose is metabolised to CO2 and H2O and ATP is generated. Contains 4 steps
Oxidation of glucose - step 1 - glycolysis
Metabolic pathway that converts glucose into pyruvic acid. During glycolysis, one glucose is converted into two pyruvate. Early in the glycolytic pathway, 2 ATP molecules consumed. In the payoff phase energy is produced. 10 water soluble cytosolic enzymes catalyse the reactions of the glycolytic pathway.
Oxidation of glucose - pyruvate oxidation and citric acid cycle - step 2
Pyruvate is transported from the cytosol across the mitochondrial membranes to the matrix. Pyruvate reacts with coenzyme A, forming CO2 and acetyl CoA. The acetyl of acetyl CoA is oxidised to CO2 via a set of 9 reactions, these reactions operate in a cycle that is called the citric acid cycle. For each acetyl group entering the cycle as acetyl CoA, two molecules of CO2 are produced. In prokaryotes pyruvate oxidation and the citric acid cycle occurs in the cytosol.
What is generated in the citric acid cycle?
3 molecules of NADH, 1 ATP/GTP, 1 molecule of FADH2. Reaction 1 includes a two carbon acetyl residue from acetyl CoA condenses with the four carbon molecule oxaloacetate to form the 6 carbon molecule citrate.
Oxidation of glucose - electron transport and PMF - step 3 where are eukaryotes and prokaryotes?
Eukaryotes localised in the internal membrane of the mitochondria and the chloroplasts. Prokaryotes electron transport chains are associated with the cell.
Oxidation of glucose - electron transport and PMF - step 3 what happens?
Transporters in the inner mitochondrial membrane allow the uptake of electrons from cytosolic NADH. Most of the free energy released during the oxidation of glucose to CO2 is retained in the coenzymes NADH and FADH2 generated during glycolysis and the citric acid cycle.
What happens in electron transport?
Cytosolic NADH+ and FADH2 generated during glycolysis and the citric cycle is oxidised to NAD+ and FAD+. Electrons are transferred from NADH+ AND FADH2 though a series of electron carriers in the inner membrane of the mitochondria (eukaryotes) or the plasma membrane (prokaryotes). Step by step transfer of electrons via the electron transport chain allows the free energy in NADH+ and FADH2 to be released in small increments and stored as the PMF.
What is the PMF?
Occurs when the cell membrane becomes energised due to electron transport reactions by the electron carriers embedded in it. Protons are pumped at several sites during ET from NADH to O2. Protons from the mitochondrial matrix are pumped across the inner mitochondrial membrane of the plasma membrane creating a proton conc gradient across the membrane
What is ATP synthase?
An enzyme complex that uses PMF to generate ATP from ADP (oxidative phosphorylation)
Where is ATP synthase in prokaryotes, mitochondria, chloroplast?
Prokaryotes - plasma membrane
Mitochondrion - inner membrane
Chloroplast - thylakoid membrane
What does ATP synthase consist of?
Membrane protein consisting of two subunits F0 and F1. Catalyses ATP synthesis on the cytosolic face of the membrane - ATP is always formed on the cytosol.
What is F0 and F1 in ATP synthase?
F0 is Hydrophobic, embedded in the membrane. Has a cavity that takes in the protons - lower portion rotates in response to ions moving down the concentration gradient across the membrane.
F1 is exposed to the cytosol, rotation of lower component of F0 activates F1 that binds and phosphorylate ADP into ATP
H+ EXOPLASMIC greater than H+ CYTOSOLIC
Oxidation of fatty acids - TAGs are hydrolysed - step 1
Fatty acids are stored as triacylglycerols (TAG), primarily as lipid droplets in eukaryotes or as free TAG in the cytoplasm of prokaryotic cells. Triacylglycerols (TAG) are hydrolysed in the cytosol to free fatty acids and glycerol
Oxidation of fatty acids - formation of fatty acyl-CoA - step 2
Occurs in cytosol, fatty acid + HSCoA + ATP -> fatty acyl CoA + AMP + PPi
Oxidation of fatty acids - transportation of fatty acyl-CoAs (carnitine transporter) - step 3
Fatty acyl-CoAs are transported into mitochondria and/or peroxisomes in eukaryotes, stay in the cytosol in prokaryotes
Oxidation of fatty acids - oxidation of fatty acyl-CoAs - step 4
Fatty acyl-CoAs can be oxidised by a) mitochondrial oxidation or b) peroxisomal oxidation. Convert fatty acyl CoA molecule to acetyl CoA and a shorter fatty acyl CoA occurs in a sequence of four enzyme catalysed reactions.
Oxidation of fatty acids - oxidation of fatty acyl-CoAs - step 4 - what happens in mitochondrial and peroxisomal oxidation
In both : one FAD molecule is reduced to FADH2, one NAD+ molecule is reduced to NADH. The cycle is repeated on the shortened fatty acyl CoA until this is completely converted to acetyl CoA. In mitochondria Acetyl-CoA enters the citric acid cycle. In peroxisomes oxidation of fatty acids yields no ATP.
Oxidation of fatty acids - ETC and PMF - step 5
Electrons from FADH2 and NADH+ are used in the ETC generating the proton motive force and resulting in synthesis of additional ATP
